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Multi-Gas Monitor (Multi-Gas Monitor) - 01.14.15

Science Objectives for Everyone
Multi-Gas Monitor is the first laser sensor to continuously measure four gases that are key for crewmembers’ health aboard the International Space Station. The multiple low-power, tunable lasers train an infrared laser beam on a cabin air sample, and sensors tuned to specific wavelengths of light detect oxygen, carbon dioxide, ammonia, and humidity. The instrument fits in a device the size of a shoebox and detects the presence of gases in less than one second.

Science Results for EveryoneInformation Pending

The following content was provided by Paul D. Mudgett, Ph.D., and is maintained in a database by the ISS Program Science Office.

Multi-Gas Monitor is the first application of laser spectroscopy technology to simultaneous measurement of multiple gases in the spacecraft cabin environment.

The Multi-Gas Monitor Tech Demo is designed to demonstrate interference free measurements of oxygen, carbon dioxide, ammonia and water vapor (humidity) without drift for a 6-month period on the International Space Station (ISS). To accomplish this primary objective, Multi-Gas Monitor is installed in NanoRacks Platform-1 or -2 in the JEM and operates continuously.

The 4 gases Multi-Gas Monitor measures are important for crew health and safety on ISS. Once Multi-Gas Monitor technology is validated in flight, the 4 gas platform can be applied to other gases of interest both for ISS and Exploration vehicles and habitats.

Description

The primary objective of Multi-Gas Monitor is to demonstrate the general suitability of tunable diode laser spectroscopy (TDLS) gas sensors onboard spacecraft. The investigation seeks to demonstrate that narrowband, low power, semiconductor lasers operating in the infrared wavelength region meet the gas detection sensitivity and specificity requirements for long term spacecraft operation on a physical platform that is likewise compatible with the space application.

Beyond that, Multi-Gas Monitor further utilizes a uniquely compelling architecture among TDLS sensors that provides for detection of multiple gases using multiple lasers in a single compact sample cell. A typical multi-gas TDLS design would use multiple independent sample cells, which greatly increase size, weight, power consumption and complexity. Multi-Gas Monitor circumvents this difficulty with the single compact sample cell that simultaneously provides optically enhanced sensitivity for all employed laser channels. Nonetheless, each laser channel sharing the common sample cell is completely independent from the other channels and is time division multiplexed. The time division multiplexing is sufficiently rapid such that a complete cycle though the suite of gases detected occurs in less than one second. The Multi-Gas Monitor design does not require collimated lasers and, thereby, eliminates a significant number of optical components and, more importantly, the necessity of aligning them while eliminating the danger of future misalignment. The optical system cannot become misaligned. Insensitivity to shock and vibration is a vital requirement for any equipment launched into space and used on a spacecraft.

The Multi-Gas Monitor design also utilizes state-of-the-art low power digital and analog electronics that allow for multiple laser channels to run for long periods of time off simple battery power. Functionality that previously required a rack of commercial instruments including function generators, lock-in amplifiers, photo detector preamplifiers, and multiple temperature and current semiconductor laser controllers has been reduced to a complete device smaller than a shoebox.

The Multi-Gas Monitor Tech Demo is designed to demonstrate continuous interference free measurements of oxygen, carbon dioxide, ammonia and water vapor (humidity) without drift for a 6 month period on the International Space Station (ISS).

Space Applications
Monitoring levels of oxygen, carbon dioxide, ammonia, and humidity is important for crewmembers’ health and safety. After the technology is verified to work long term in the ISS environment, the platform can be adapted to other gases, including dangerous combustion byproducts like carbon monoxide. Future space exploration vehicles and habitats would benefit from similar low-power, real-time air sensors.

Earth Applications
Portable, low-power instruments that detect small concentrations of multiple gases at a time could be useful in power plant pollution monitors, atmospheric research, and food quality assurance. Tunable laser sensors can also be used in breath-based medical diagnostics and for workplace safety in industrial settings.

Operational Requirements
One crew member is required for all investigation requirements including installation, activation, checkout, comparing with other hand-held units available on ISS, making measurements in battery powered hand-held mode, and mounting to Express Rack for the usability demonstration. The NanoRacks Platform operations, data downlink is on a weekly basis. For the hand-held survey, data is called down as the crewmember transports Multi-Gas Monitor to 6 to 8 predetermined USOS locations for a 3-5 minute analysis of the air in each location. For the Express Rack deployed mode (over several days), initial and final data is called down, but the majority is downlinked upon return of Multi-Gas Monitor to the NanoRacks Platform (all data is recorded internally). No samples are collected or returned. No hardware is returned unless a malfunction occurs and down mass can be successfully negotiated.

Operational Protocols
Procedures include steps for destowing Multi-Gas Monitor, connecting cables and installing Multi-Gas Monitor at the front face of the NanoRacks Platform, using the control buttons, powering on, reading the display, acquiring spectra, testing to verify that Multi-Gas Monitor is in fact working properly, powering down while installed in the NanoRacks Platform, and removal from the NanoRacks Platform. Procedures also cover the other deployment modes—the crew hand-held survey of USOS using Multi-Gas Monitor and for mounting and connecting Multi-Gas Monitor to Express Rack power in the US Laboratory. The procedural steps to downlink Multi-Gas Monitor data are already covered by existing NanoRacks Platform documentation.